Geography and Oceanography of the Bay of Bengal with Drainage Basins

The Global International Waters Assessment (GIWA) subregion 53, Bay of Bengal (Fig. 1) includes the Bay of Bengal Large Marine Ecosystem (BOBLME) (1), and associated watersheds. The nations of Bangladesh, Bhutan, Maldives, Myanmar, Nepal and Sri Lanka are all in the Bay of Bengal Subregion (BOBSR). The major land area of India, a relatively minor part of Indonesia (eastern Sumatra), western Peninsular Malaysia, and the western part of southern Thailand are included. The Tibetan Plateau of the People’s Republic of China occupies the northernmost part of the BOBSR. Three major transboundary river systems significant to the BOBSR originate in the Tibetan Plateau. The estimated land area of BOBSR is about 4 mill. km2 must of which is in India (Table 1). In addition to the 2 large islands, Sri Lanka and Sumatra, numerous small islands, some inhabited, but the majority uninhabited, are part of the BOBSR. Some islands are simply coral atolls, while others have significant mangrove ecosystems. The Indonesian island of Sumatra and the Indian Andaman and Nicobar Islands are volcanic. The physiography of the BOBSR ranges from the high Himalayan peaks to coastal plains, with similar profiles traversing Myanmar. The elevation of Peninsular Malaysia, southern Thailand, eastern Sumatra and Sri Lanka ranges from heights of between 1000–3000 m descending to coastal plains. The Maldives consist entirely of atolls of elevations of less than 3 m. The Bay of Bengal is a relatively shallow embayment of the northeastern Indian Ocean, occupying an area of 2 173 000 km2 (2). The Andaman Sea is a subsection of the Bay of Bengal. The Malacca Straits, extending from the Andaman Sea until but excluding Singapore, is also a part of the BOBSR (Fig. 1). The tropical climate of the BOBSR is strongly influenced by the monsoons. A highly complex, seasonally reversing current system, linked to the Arabian Sea and influenced by the Southwestand Northeast Monsoons, exists in the Bay of Bengal (3). However, a contrary view holds that the Bay of Bengal differs from the Arabian Sea in maintaining a clockwise circulation of major currents during both monsoons (4). The coastline of the Bay of Bengal is influenced mainly by the Southwest Monsoon which brings heavy rain. The inflow of freshwater from the major subcontinental rivers coupled with monsoonal rainfall depresses salinity in the coastal waters. This is compensated for by water with higher salinity from the Indian Ocean, which is driven northward during the Southwest Monsoons. The primary Issues of Livelihood, Sustainable Development, and Governance: Bay of Bengal